Microparticulated whey protein (MWP) is a fat replacer; manufactured from whey protein concentrate in a process that primarily involves simultaneous heating and shearing. Alternative processes may be utilized instead, such as extrusion cooking at acid pH or dynamic high pressure shearing, i.e., microfluidization. The result is whey protein aggregates with particle sizes that usually range between 0.1 and 10 mm (Spiegel & Huss, 2002) and that have previously shown their ability to provide sensory sensations associated with the presence of milk fat, i.e., creaminess, when incorporated into low-fat stirred yoghurt. Regarding the rheological charac- teristics of yoghurts when MWP is included in the formulation, improvements of the texture in reduced fat set-style yoghurts have been reported. Whether these microparticles act as active or inert fillers in the yoghurt network has not been completely elucidated. Based on microstruc- tural studies, several authors have suggested that they do not interact actively with the casein micelles and other whey proteins, as homogenized fat globules do in full fat yoghurt.